Grade School2026-05-01

My Solution: Exercism Grade School solution

Instructions

Build a school roster that keeps students grouped by grade and returns names in alphabetical order within each grade.

Rules:

• add_student(name, grade) adds a student unless that student name was already enrolled.
• roster() returns all students ordered first by grade, then alphabetically within each grade.
• grade(number) returns the students in that grade in alphabetical order.
• added() returns the history of whether each attempted add succeeded.

Solution

class School:
    def __init__(self):
        self.db = {}
        self.enrolled_students = set()
        self.added_list = []
        
    def add_student(self, name, grade):
        if name not in self.enrolled_students:
            self.enrolled_students.add(name)
            self.db.setdefault(grade, []).append(name)
            self.added_list.append(True)
        else:
            self.added_list.append(False)

    def roster(self):
        roster = []
        for grade in sorted(self.db.keys()):
            roster.extend(sorted(self.db[grade]))

        return roster
        
    def grade(self, grade_number):
        return sorted(self.db.get(grade_number, []))
        
    def added(self):
        return self.added_list

Syntax Notes

• A dictionary groups student names by grade.
• self.db.setdefault(grade, []) creates an empty list for a grade only if it does not exist yet, then returns that list so .append(name) works in one step.
• A set tracks which names have already been enrolled.
• roster() sorts by grade first, then sorts each grade's names alphabetically.
• grade() reads one grade directly from the dictionary and sorts the result.
• added() returns the boolean success history for each enrollment attempt.